Rupert Murdoch's 21st Century Fox on Wednesday revealed it had increased a takeover offer for pan-European TV group Sky, valuing the group at £24.5 billion and trumping Comcast's rival offer.

21st Century Fox's improved bid is for the 61 per cent of Sky it does not own.

New York-listed 21CF raised its offer to 14 for each outstanding share, up substantially on a previous bid of 10.75.

Following the announcement, Sky's share price was down 1.3 per cent at 14.81, though above the improved offer.

“Today, 21CF and the Independent Committee of Sky are pleased to announce that they have reached agreement on an increased... cash offer,” a statement said on Wednesday.

Fox's new bid values the whole of Sky at £24.5 billion, beating an offer of £22 billion from United States (US) cable giant Comcast for the satellite TV group.

Fox's long-running pursuit for all of Sky has been plagued by UK government fears over media plurality and broadcasting standards and the influence of Australian-born US citizen Murdoch.

Murdoch owns major British newspaper titles The Times and The Sun and critics say obtaining full control also of the rolling television channel Sky News would give him too much influence in the news business.

To remedy this, Fox has proposed to sell Sky News to Disney as part of a full takeover.

The pursuit for Sky is meanwhile further complicated by a battle between Walt Disney and Comcast for key assets of 21st Century Fox.

Should Disney succeed, it will obtain Fox's 39 per cent stake in Sky as part of the package.

Sky's jewel in the crown is its live coverage of English Premier League football, while the group also provides broadband internet and telephone services.

Sky changed its name from BSkyB after agreeing in 2014 to buy Sky Italia and a majority holding in Sky Deutschland.

In 2011, Murdoch was forced to abandon a takeover bid for BSkyB as controversy raged over the hacking of celebrities and crime victims by his tabloid the News of the World, which was subsequently shut down.